This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource.
Offshore systems typically include one or more subsea wellheads located at the sea floor. To connect the subsea wellheads to a floating rig (e.g., drill ship, semi-submersible, floating drilling platform, floating production platform, etc.) located at the water surface, a telescoping joint is employed to compensate for surface wave action. The telescoping joint typically is an assembly of an inner tubular surrounded by an outer tubular. The inner and outer tubulars move axially relative to each other to compensate for the required change in the length of the riser string as the floating rig experiences surge, sway and heave.
The telescoping joint is located above the top section of the riser string. The riser string runs from the telescoping joint down to various pressure control equipment packages, such as a lower marine riser package and/or a blowout preventor stack. The pressure control equipment is in place to seal, control and monitor the wellbore. The pressure control equipment is coupled to the subsea wellhead by way of a wellhead connector. The wellhead connector provides bending capacity for the entire assembly. Fluid within the riser flows up through the riser and the inner tubular to a diverter assembly located at the floating rig. The diverter assembly includes a diverter for diverting mud and cuttings, and a flex joint.
Telescoping joints typically include a sealing means in the annular space between the inner and outer tubulars to seal off the fluid contained in the riser. The sealing means is commonly referred to as a “packer” or “packer assembly.” The packer assembly prevents fluid or mud loss from the outer tubular into the external environment. Traditionally, telescoping joint packer assemblies included two seals, which are radially energized with air or hydraulics, for forming dynamic seals between the inner tubular and the outer tubular.
An issue with existing packer assemblies is the uncertainty in the wear of the packer assembly seals. Because existing packer assembly seals are radially energized by pressure, either air or hydraulically applied, the load distribution over the packer to inner tubular surface may be uneven. Uneven load distribution results in uneven seal wear and unpredictable seal life.
Because of this uncertainty, existing packer assemblies include two seals. When one seal fails, the other seal functions as a backup seal. After one seal fails, the entire packer assembly must be replaced in order to ensure that backup seal does not fail, exposing the fluid from the riser to the external environment. To replace existing packer assemblies, any fluid in the riser string (e.g., mud) must be circulated out of the riser string. Then a controlled disconnect of the lower marine riser package from the blowout preventor stack is performed. Next, the diverter assembly is removed and the tensioning equipment must be stored before the packer assembly can be landed on a riser spider in a hard hang-off. Only then can the packer assembly seals be replaced, which can take as much or more than ten hours of time. After replacing the seals, the entire process is reversed. With operating expenses at hundreds of thousands of dollars a day and more, packer assembly seal failure results in considerable expenses.
Accordingly, a telescoping joint packer assembly with more reliable and predictable seal wear is desired.